In the field of graphic arts, an image-forming system exhibiting photographic characteristics of super-high contrast (in particular, at least 10 in gamma) is necessary for improving the reproduction of continuous tone images by dot images or the reproduction of line images.
Prior to the present invention, lith, a specific developer has been used to achieved super-high contrast. Lith developer contains hydroquinone only as the developing agent. The concentration of a free sufite ion is greatly reduced in the lith developer (usually less than 0.1 mol/liter) because the sulfite is used as a preservative in the form of an addition product with formaldehyde so as not to obstruct the infectious developing property thereof. Therefore, the lith developer has serious faults in that the lith developer is very liable to oxidation and thus can not be stored for more than 3 days.
As processes of obtaining high-contrast photographic characteristics using a stable developer, include those processes utilizing hydrazine derivative. These processes are described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,211,857, and 4,243,739. According to the processes, photographic characteristics having super-high contrast and high sensitivity are obtained. Further, since sulfite may be added to the developer at a high concentration, the stability of the developer to air oxidation is greatly improved.
On the other hand, various new light sources (e.g., light emitting diode (LED), He-Ne laser, and argon laser) for the light exposure of photographic light-sensitive materials have been developed and practically used. It is necessary to select proper spectral sensitizing dyes for photographic light-sensitive materials having optimum spectral sensitivity for the spectral energy distribution of such a light source. Also, such a technique has been practiced utilizing a lith developer. That is, in the aforesaid image-forming system for obtaining photographic light-sensitive materials exhibiting photographic characteristics of high contrast by utilizing a stable developer which includes a hydrazine derivative, the increase of sensitivity and contrast is accelerated. Further, the D.sub.max, i.e., maximum density (described below) is increased by the use of a cationic compound in the photographic light-sensitive material as described in JP-A Nos. 60-140340 and 61-167939.
In regard to spectral sensitizing dyes, the use of a cationic dye as the spectral sensitizing dye gives a higher D.sub.max than the utilization of an anionic dye and/or a betaine dye.
However, the use of a cationic dye is accompanied by an undesirable phenomenon. More specifically, there is an increase in the formation of small black spots, so-called "black pepper" on the developed photographic light-sensitive material. This increase becomes a serious problem, especially during a photo-engraving step.
Accordingly, efforts have been made for inhibiting the formation of black peppers while maintaining high D.sub.max and using a cationic dye as the spectral sensitizing dye.
As a means for inhibiting the formation of black peppers, JP-A No. 62-25745 discloses a means for reducing the pH of the film surface below 5.8 using an organic acid such as ascorbic acid, acetic acid, citric acid, or salicylic acid. However, by reducing the pH alone, it is impossible to completely inhibit the formation of black peppers. Further, reducing the pH hinders the hardening of the silver halide photographic emulsion layers, whereby the emulsion layers are liable to scratching.